1. Field of the Invention
The present invention relates to a compact lens barrel mechanism suitable for an optical lens system having relatively shiftable lens groups and more particularly to a lens barrel mechanism for relatively shifting the lens group in a linear movement along the optical axis to accomplish two or more modes of operation.
2. Description of the Prior Art
The prior art is quite familiar with various forms of lens barrel mechanism for mechanically shifting relative groups of lens. Quite frequently, the lens barrel mechanisms will rotate the lens groups in a spiral or helicoidal movement along the optical axis. As can be appreciated, lenses moved in this fashion must be carefully centered and aligned to maintain a correct position on the optical axis regardless of the relative movement. For example, U.S. Pat. No. 3,904,275 is of interest in showing a lens barrel mechanism for moving a front and rear lens group.
Additionally, it is known that a soft focus condition can improve certain pictures.
The prior art is still striving to optimize the design of lenses with the most compact lens barrel mechanism that is economically and physically capable of being utilized. The consumer market is demanding light and more compact lenses at commercially acceptable prices. Accordingly, there is still a need in the prior art to optimize a lens barrel mechanism within these parameters.